Recently in the field of video input, the number of pixels of cameras for mobile phones and digital still cameras is increasing and the pixel pitch thereof is decreasing.
Various spatial resolutions are used for different levels of image quality required for various imaging devices. For example, the resolution of TV phones is of a relatively small number of pixels; for example, approximately QCIF (Quarter Common Intermediate Format; 176 pixels horizontally and 144 pixels vertically) or approximately QVGA (Quarter Video Graphics Array, 320 pixels horizontally and 144 pixels vertically). By contrast, the resolution of digital single-lens reflex cameras exceeds 10 million pixels.
Various temporal resolutions are also used for different levels of image quality. For example, regarding the temporal resolution of up to the number of pixels of HDTVs, imaging is performed at the video rate of consumer devices (30 frames/sec.). By contrast, for performing imaging at a greater number of pixels, the frame rate is merely several frames per second at the maximum, which is realized by the consecutive shooting function provided by digital still cameras.
Meanwhile, in the field of video display, flat TVs are rapidly spreading. In accordance with this, users are expected to view video materials by a combination of a camera and a display of various resolutions in the future.
Comparing the temporal and spatial resolutions of the camera on the input side (“temporal and spatial resolutions” means temporal resolution and spatial resolution; the same is also applied below) and the temporal and spatial resolutions of the display on the output side, the temporal and spatial resolutions of the display on the output side are higher in the currently available consumer devices. Therefore, general users today cannot easily obtain a video material which allows the device on the output side to make the maximum use of the performance thereof.
A reason why such a situation has occurred is that the reading speed is conventionally the bottleneck. The imaging at a high spatial resolution is limited to being performed at 5 frames per second, whereas the imaging at 30 frames per second is limited to being performed at the spatial resolution of HDTVs. For this reason, it is conventionally difficult to perform imaging at a high spatial resolution and a high frame rate.
In order to address the above-described problems, Patent Documents 1 through 3, for example, propose a method for providing both a high spatial resolution and a high frame rate, by which images having different temporal resolutions and different spatial resolutions are input from cameras of two systems to generate an image having a high spatial resolution and a high frame rate by signal processing. These patent documents describe a structure shown in FIG. 18.
FIG. 18 shows a structure of a conventional imaging device. Light incident on the imaging device is partially transmitted through a half mirror 171 and incident on a first camera 172. As a result, a moving image having a low resolution and a high frame rate is taken. Light which is incident on the imaging device and reflected by the half mirror 171 is incident on a second camera 173. As a result, a moving image having a high resolution and a low frame rate is taken.
An upconverter 174 receives the moving images taken by the first camera 172 and the second camera 173 and performs image processing to output a moving image having a high resolution and a high frame rate.
Patent Document 1: Japanese Laid-Open Patent Publication No. 7-143439
Patent Document 2: PCT Japanese National Phase Laid-Open Patent Publication No. 2005-515675
Patent Document 3: Japanese Laid-Open Patent Publication No. 2005-318548